For a long time, it seemed as if a medical discovery that Science called "one of the greatest of 2007" might never get covered by the mainstream media because it was just too complicated. But then an enterprising journalist and artist with the Philadelphia Inquirer boldly went where no reporters dared go. Writer Tom Avril and artist Cynthia Greer figured out how to simplify this complicated discovery into a completely-accurate cartoon (pictured).

A researcher named Steven Reiner at University of Pennsylvania proved that the human body fights disease with two kinds of immune cells (called T-cells): some that fight the invading microbes, and some that exist just to keep a record of how to fight those microbes in the future. Those "memory" cells are what this researcher revealed, and their mysteries are still being unlocked.

Writes Avril:

The University of Pennsylvania physician electrified his field last year by showing how the immune system generates two types of the sophisticated tools known as T-cells: one to fight invaders to the death, the other to remember the battle plan for the next time the same enemy shows up.

Reiner's finding, made with John Chang, Vikram Palanivel and colleagues, was named one of the top 10 breakthroughs of 2007 by the journal Science. Using mice, the team provided evidence that T-cells arise from a self-renewing process a bit like that used by stem cells. Without it, we'd fight off a bug once, and the next time we'd be dead.

"It's an amazing system," Reiner marvels. "You do use these cells, but you don't deplete them. That's how we can live long lives with short-lived cells."